Question about 3d objects.

[Tdata]

Okay my question is, if you place a 3d cube on the ground, and want find out what faces are free, IE not connected to any other block, what is the best way to go about it?

 

[Brewmeister]

What are the degrees of freedom? If the blocks are static, and aligned, then an iterative cycle of all block positions checking X+1, X-1, Y+1 & Y-1 would do it.
If the cube is free to move & rotate, then a Ray Tracing algorithm might be appropriate.